Process parameters optimization and molecular studies on bacteriocin-producing lactic acid bacteria from ‘Kati’

This work described the isolation and identification of bacteriocin-producing lactic acid bacteria (LAB) from ‘Kati’(a sorghum based fermented food), and to evaluate the antibacterial effect of bacteriocin on selected pathogenic bacteria. The identities of the isolates were revealed to be as Lactobacillus plantarum, L. brevis, L. fermentum KAT1, L. fermentum KAT2 and Lactococcus lactis using 16S rRNA gene sequence analysis. Out of 28 LAB, five were found to inhibit selected pathogenic bacteria namely; Escherichia coli, Staphylococcus aureus, Salmonella typhimurium and Bacillus cereus. The unpurified bacteriocins produced by the isolated LAB were characterized with respect to the effect of temperature, pH and surfactant. The test isolates showed activities of 6400, 6400, 6400, 3200 and 1600 AU/ml respectively. Crude bacteriocin from L. brevis and L. lactis were the most heat stable at 121ºC for 60 min. Bacteriocins from L. plantarum, L. lactis and L. fermentum KAT1 showed the highest antibacterial activity and stability at pH 2.0 to 6.0. Exposure to Tween 20 increased the bacteriocin activity of the LAB isolates except for L. fermentum KAT2 where loss of activity occurred. The findings from this study suggest that bacteriocinogenic LAB present in ‘kati’ have potentials to inhibit pathogenic/spoilage microorganisms in foods.